1. Field of the Invention
This invention relates generally to a signal transmitting system and more particularly is directed to improvements in a signal transmitting system including an analog to digital (A-D) converter and a digital to analog (D-A) converter.
2. Description of the Prior Art
In a prior art signal transmitting system for an analog signal, A-D and D-A converters are used in combination. For example, in such a system, an A-D coverter is used in the transmitter side of the system for converting an analog input signal to a digital signal, and this digital signal is transmitted through a suitable signal handling circuit, such as, a digital memory circuit, to a D-A converter in the receiver side of the system where the digital signal is decoded or demodulated and an analog output signal corresponding to the analog input signal is again obtained.
Such a system is very useful in the field of signal transmission, because the digital signal derived from the A-D converter is easily handled by means of various types of signal transmission.
However, as the analog input signal is twice converted in the A-D and D-A converters, the waveform of the analog output signal is apt to be deformed or does not precisely correspond to that of the analog input signal. Therefore, the fidelity of the system is apt to be insufficient.
In the known system, such deformation in the waveform of the analog output signal is sought to be minimized that is, the fidelity of the system is improved, by increasing the number of digital levels and digital bits in the A-D and D-A converters.
However, the complexity, cost and bulk of the system are all undesirably increased when the numbers of the digital levels and digital bits in the A-D and D-A converters are increased.